The Order History Tab displays a single line item that details the Date, ID Number, Transaction Number, Transaction Type, PO Number and Transaction Total of the current Invoice. All these fields are read only and can be changed in the General Tab of the Invoice.
At the bottom left of the form, the Payment Information section will display the amount of money the customer has paid against the Invoice to date and the credit card information you have already provided in the Customers form. It is worthwhile to briefly review the information before posting the invoice.
Background on toolbar buttons such as Post, Customer, Receivable, can be reviewed in the Invoice Overview help section. See: Invoices Overview.